Preparation And Evaluation Of Water-Storing Coated Urea Fertilizers

Either fertilizer or water is important factors which influence crop production. However, firstly, the lower recovery and higher losses of conventional fertilizer are great problem which influence crop production efficiency and the safety of agricultural environment. Slow/controlled release fertilizers are efficient technology to increase fertilizer recovery and reduce fertilizer losses. Secondly, the pressure of agricultural water-saving is ever-increasing due to the crisis of fresh water resources in our country. And, the application of hydrogels to dryland or water-saving agriculture is one of important water-saving technology. By incorporating fertilizers and hydrogels into one form, developing water-storing slow/controlled release fertilizers is one of heavy technology to increasing efficiency of fertilizer and water, and the water-storing slow/controlled release fertilizers (or gel-based slow release fertilizers) is international new direction to fertilizer research. In this thesis, a new technology of preparation of water-storing coated urea(WSCU), whose coating directly forms on the surface of urea granular by polymerization, was invented, and evaluation was given on performance and biological effects of WSCU with using experimental method such as physical and chemical test, biology and isotope tracer. Some results and conclusions are as follows as.A newly preparation technology of WSCU, whose coating directly forms on the surface of urea granular by polymerization in native solution, was invented. And the surface of urea granular successfully coated by a potassium-type hydrogels using this coating technique, and newly type of WSCU had been made out. The advantages of the technique are nonusing organic solvent, no pollution, and low cost.The results of measurements of potassium-type hydrogels indicate that the coating of WSCU own such advantages as high abrasion-resistant, high water absorbency (30g/g, based on dry coating weight), low hygroscopy.The results of SEM photography of WSCU indicate that the coating texture of potassium-type gel coated urea is dense, and the crystal of gels is tightly felted on surface of urea crystal which is contributed to the abrasion-resistant performance of WSCU's coaling. The interpreting results of IR spectra of WSCU's coatings indicate that the coating of potassium-type hydrogels associated with urea crystal by hydrogen bond or chemical combination, of which disclose chemistry nature of abrasion -resistant of the coating of WSCU.The results of 7 Day solution rate test indicate that the WSCU delay nutrient release of urea which is mainly depended on absorption of hydrogels to urea, and the slow release effects of WSCU on urea is less than that of (water-storing polymer+plastic) coated urea on urea. Thus, the effects of nutrient slow/controlled release of gel coating need to be improved.The results of measurements of soils treated by WSCU indicate that the water-absorbing capacity of soils is improved because of application of WSCU to soils, and the evaporation of soil water was depressed, the availability of soil water increased. What the effects of WSCU improved soil water owe to the contribution of gel coating of WSCUThe short-term experimental results of Chinese cabbage in greenhouse indicate that the biomass of Chinese cabbage increased because of application of WSCU to soils. The analysis results of nutrient concentrations in Chinese cabbage plant indicate that the uptake of nitrogen and phosphorus in plant were increased significantly, and the uptake of plant potassium increase unsignificantly. The results of 15N-labelled urea tracer experiment indicate that absorption amount of urea in soil increased because of application of WSCU, the nitrogen losses of soil decreased when WSCU applied to soils, the nitrogen recovery was increased.To sum up, the preparation technology of WSCU which coating directly form on the surface of urea granular by polymerization in native solution is a creative technology, the advantages of which are nonusing organic solvent,...